The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In a laser printer, printing is achieved by first scanning a digitized image onto an optical photoconductor (OPC). Typically, the scanning is performed with diodes, e.g. laser diodes or light emitting diodes that pulse a beam of energy onto the optical photoconductor. The optical photoconductor typically comprises a movable surface coated with a photoconductive material capable of retaining localized electrical charges. The surface of the optical photoconductor is a continuous area where the surface is logically considered to be divided into small units called pixels. Each pixel is capable of being charged to a given electrical potential, somewhat independent of the electrical charge of each surrounding pixel.
In operation, the pixels are first charged to a base electrical charge as the pixels move past a charging unit during each revolution of the optical photoconductor. Then, as the pixels move past the laser diodes, a beam of energy, e.g. a laser, is pulsed to remove electrical charge from selected pixels. The unaltered and altered pixels thus form an image on the optical photoconductor. One portion of pixels will attract toner, while the other portion will not based on various factors such as the electrical potential of the toner. However, since the lasers have a Gaussian beam intensity shape, the edges of the lasers do extend past the logical rectangular pixel location so adjacent pixels do interact to a certain extent.
The toner is then transferred to a print medium, e.g. paper, transparency, and fabric. After the toner is transferred to the print medium, the toner is affixed thereto. Any residual toner on the equipment is then removed by a cleaning station.
Generally, laser printing devices include multiple laser diodes to create multiple lasers for printing as previously described. Images are printed by moving at least one of the optical photoconductor and/or the laser diodes relative to one another repeatedly, thus resulting in sweeping of the lasers relative to the optical photoconductor. The print medium and the optical photoconductor are also moved relative to one another to print the image onto the print medium. Mirrors are often used between the laser diodes and the optical photoconductor.
FIG. 4 schematically represents a set of printed lines 400 created by three sweeps of lasers associated with eight laser diodes. In the example of FIG. 4, each sweep of the eight laser diodes causes eight corresponding lines to be created as represented by lines 1-8. Undesirable visual artifacts, such as gaps or overlaps, can occur in between sweeps of the lasers. For example, as shown in FIG. 4, a gap 402 exists in between (i) the eighth printed line created during the first sweep of the lasers and (ii) the first printed line created during the second sweep of the lasers. Also, an overlap 404 is present in between (i) the eighth line created during the second sweep of the lasers and (ii) the first printed line created during the third sweep of the lasers.